When growing agricultural crops, a variety of agricultural chemicals are sprayed sometimes, for disease prevention, pest control and increased yield. Most of the agricultural chemicals are organic chemical compounds which include, within their molecules, a specific chemical structure that determines their characteristic behaviors as the chemical. A large number of these agricultural chemicals are highly toxic not only to pest insects and viruses but also to human bodies. Further, agricultural chemicals have strong influences on the ecology in the agricultural fields and their surroundings, and potentially destructive to the ecology. For these reasons, the molecular structure of agricultural chemicals is designed so that the agricultural chemicals will decompose naturally with the elapse of time.
However, such a natural decomposition of agricultural chemicals is usually a slow process. Therefore, if there is only a short period of time between the high season of a pest and the harvesting season of an agricultural crop, most of the necessary amount of the agricultural chemical which is applied on time is not decomposed before the harvesting season, and the crop would have to be harvested with a large amount of the agricultural chemical still attached as residual agricultural chemical. In view of safety for human bodies and others, it is not preferable that agricultural crops are shipped with residual agricultural chemicals. In order to reduce the amount of residual agricultural chemicals at the time of harvest, sometimes the agricultural chemicals are applied before the pest season. However, natural decomposition of agricultural chemicals begins right after the application, so if the application is made earlier than the outbreak timing, necessary amount of the agricultural chemical will not be present at the outbreak of the pest nor during the time of spread thereafter. In this case, it is impossible to achieve satisfying effects with the agricultural chemical. As described, according to the conventional agricultural chemical technology, it is difficult to let agricultural chemicals exhibit satisfying effects and to reduce residual agricultural chemicals.